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Bacteria : 



H practical Stu^^ in Btolocjp. 



Definition. 



lOLOGY is the science of living things : — (S^og — life, 

 Xoyog — science. It may be divided into two 

 branches, each of which corresponds to a distinc- 

 tive mark of living things. They may be recognised 

 — (i) By their form — Morphology; (2) by their 

 ^^'^^^r effects (movements and mutual actions, chemical) — 

 ^%ij%<^^ Physiology. The simplest possible organism is 

 H. y^Y V Torula^ the single cell of Saccharomyces^ or Yeast. 

 There is no well-defined limit between ferments 

 and fungi, or, again, between fungi and bacteria. Their smaller 

 size is the principal difference which separates bacteria from 

 ferments, since in other respects these two classes are for the most 

 part alike in form and organisation. Everyone now speaks of 

 microbes, yet few of those who make use of the term have any 

 clear conception of the organisms in question, or could give an exact 

 account of the function which microbes fulfil in nature. And yet 

 this function concerns us all. There is much to be done before 

 modern society is practically on a level with the achievements of 

 science ; many prejudices must be uprooted and many false 

 notions must be replaced by those which are sounder and more 

 just. 



In order to indicate the organisms which produce diseases, 

 the English and Germans use the word Bacteria, which is only 

 the name of one of the peculiar species assigned to this group, 

 and the one with which we have been longest acquainted. In 

 this case the name is generalised and applied to the entire group. 

 The Italian authors who have been recently occupied with the 

 study of microbes have on their part adopted the name Protista, 

 proposed by Haeckel, and of which the sense, although not the 

 etymology, is almost the same as that of the word Microbe^ which 

 is the French term for Bacteria, and only signifies a small living 

 being. It decides nothing as to the animal or vegetable nature 



Journal of Microscopy and Natural Science. 



New Series. Vol. III. 1890. m 



